CVE-2026-44819 Overview
CVE-2026-44819 is a heap-based buffer overflow vulnerability in Microsoft Office that allows an unauthorized attacker to execute code locally. The flaw is classified under [CWE-122] (Heap-based Buffer Overflow) and requires user interaction to trigger. An attacker crafts a malicious Office document that, when opened by a victim, corrupts heap memory and enables arbitrary code execution in the context of the current user.
Critical Impact
Successful exploitation grants the attacker code execution on the target system with the privileges of the user opening the malicious document, impacting confidentiality, integrity, and availability.
Affected Products
- Microsoft Office (specific versions enumerated in the Microsoft Security Update CVE-2026-44819)
Discovery Timeline
- 2026-06-09 - CVE-2026-44819 published to NVD
- 2026-06-09 - Last updated in NVD database
Technical Details for CVE-2026-44819
Vulnerability Analysis
The vulnerability is a heap-based buffer overflow within Microsoft Office document parsing logic. When Office processes a specially crafted file, an undersized heap allocation receives more data than its capacity permits. The overflow overwrites adjacent heap metadata or object pointers, allowing an attacker to influence program control flow.
Exploitation requires the victim to open a malicious file delivered through email, a network share, or a download. The attack vector is local and the privileges required are none, but user interaction is mandatory. Successful exploitation yields arbitrary code execution with the privileges of the logged-on user, with high impact to confidentiality, integrity, and availability.
At publication time, no public proof-of-concept exists and the CVE is not listed in the CISA Known Exploited Vulnerabilities catalog. The EPSS score is 0.079%, reflecting a low predicted likelihood of near-term exploitation.
Root Cause
The root cause is improper bounds validation during heap allocation and copy operations within Office's file parser. Length fields embedded in the document are trusted without verifying that the destination heap buffer can hold the supplied data, satisfying the conditions for [CWE-122].
Attack Vector
An attacker delivers a weaponized Office document to a target user. When the user opens the file, the malformed structure triggers the overflow during parsing. The corrupted heap state is then leveraged to hijack execution and run attacker-controlled payloads inside the Office process. See the Microsoft Security Update CVE-2026-44819 advisory for product-specific details.
Detection Methods for CVE-2026-44819
Indicators of Compromise
- Office processes such as winword.exe, excel.exe, or powerpnt.exe spawning unexpected child processes including cmd.exe, powershell.exe, rundll32.exe, or mshta.exe.
- Office applications crashing or generating Windows Error Reporting events shortly after opening attachments from email or external sources.
- Outbound network connections initiated by Office processes to previously unseen domains or IP addresses.
Detection Strategies
- Monitor for anomalous parent-child process relationships originating from Office binaries, a high-fidelity signal for document-based exploitation.
- Inspect Office telemetry for repeated process crashes correlated with specific document hashes or senders.
- Apply YARA or content rules to email and file storage gateways to flag malformed Office files containing oversized embedded structures.
Monitoring Recommendations
- Forward Microsoft-Windows-Sysmon process creation, image load, and network events from endpoints running Office to a centralized analytics platform.
- Track Office add-in and template directory writes, which attackers frequently abuse for persistence after initial code execution.
- Alert on macro execution and Protected View bypass events surfaced in the Office security audit log.
How to Mitigate CVE-2026-44819
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft Security Update CVE-2026-44819 advisory to all affected Office installations.
- Prioritize patching on workstations that routinely process external documents, including finance, HR, and executive endpoints.
- Block inbound Office attachments from untrusted senders at the email gateway until patches are deployed.
Patch Information
Microsoft has released a security update addressing CVE-2026-44819. Administrators should consult the Microsoft Security Update CVE-2026-44819 page for the list of affected products, build numbers, and KB articles, then deploy the update through Windows Update, Microsoft Update, or enterprise patch management tooling.
Workarounds
- Enforce Protected View and Office Application Guard for documents originating from the internet or email.
- Disable legacy file format support such as .doc, .xls, and .ppt where business requirements allow.
- Apply Attack Surface Reduction (ASR) rules to block Office applications from creating child processes and from injecting code into other processes.
# Enable ASR rules that block Office child processes and code injection
Set-MpPreference -AttackSurfaceReductionRules_Ids `
D4F940AB-401B-4EFC-AADC-AD5F3C50688A,`
75668C1F-73B5-4CF0-BB93-3ECF5CB7CC84 `
-AttackSurfaceReductionRules_Actions Enabled,Enabled
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
